Hearing devices are wearable hearing apparatuses which are used to assist the hard-of-hearing. In order to accommodate numerous individual requirements, various types of hearing devices are available such as behind-the-ear (BTE) hearing devices, hearing device with an external receiver (RIC: receiver in the canal) and in-the-ear (ITE) hearing devices, for example also concha hearing devices or completely-in-the-canal (ITE, CIC) hearing devices. The hearing devices listed as examples are worn on the outer ear or in the auditory canal. Bone conduction hearing aids, implantable or vibrotactile hearing aids are also available on the market. The damaged hearing is thus stimulated either mechanically or electrically.
The key components of hearing devices are principally an input converter, an amplifier and an output converter. The input converter is normally a receiving transducer e.g. a microphone and/or an electromagnetic receiver, e.g. an induction coil. The output converter is most frequently realized as an electroacoustic converter e.g. a miniature loudspeaker, or as an electromechanical converter e.g. a bone conduction hearing aid. The amplifier is usually integrated into a signal processing unit. This basic configuration is illustrated in FIG. 1 using the example of a behind-the-ear hearing device. One or a plurality of microphones 2 for recording ambient sound are built into a hearing device housing 1 to be worn behind the ear. A signal processing unit 3 which is also integrated into the hearing device housing 1 processes and amplifies the microphone signals. The output signal for the signal processing unit 3 is transmitted to a loudspeaker or receiver 4, which outputs an acoustic signal. Sound is transmitted through a sound tube, which is affixed in the auditory canal by means of an otoplastic, to the device wearer's eardrum. Power for the hearing device and in particular for the signal processing unit 3 is supplied by means of a battery 5 which is also integrated in the hearing device housing 1.
Hearing devices would have typically not have been able to be sealed hermetically, since the membranes of the microphone and the receiver were pretensioned by the difference of the outer and inner air pressure. The term “membrane” is understood here to mean an electroacoustically active membrane or also the cover membrane for protection against the penetration of fluid and/or particles.
The outer air pressure depends on the height above sea level, on the meteorological conditions and on the temperature, while the pressure on the inside of the membrane would remain the same in the case of a closed converter housing and constant temperature. As a result, a force would be exerted on the membrane, which may also lead to damage to the converter.
The microphone and loudspeaker thus have an air equalization opening, so that both sides of the membrane experience the same pressure. The hearing device housing is connected to the outer region by way of an additional gas-permeable membrane. The disadvantage of this construction is that steam can reach the inner region of the hearing device through the membrane and can thus also reach the converter itself by way of the air equalization opening. If the steam condenses, the sensitive metal parts may corrode.
The patent application DE 10 2006 008 044 B3 discloses a hearing aid device which can be worn in the ear and comprising a ventilation channel. The barometric pressure equalization in a sound channel between a receiver and a cerumen protection facility with a gastight membrane is achieved by a pressure equalization channel, which opens into the sound channel. The pressure equalization channel connects the sound channel to the outer region and/or a ventilation channel.